In the above connection structure, a terminal part of the device substrate and a terminal part of the flexible circuit substrate are electrically connected through conductive particles included in the ACF. More specifically, as illustrated in FIG. 9A, an ACF 830 is positioned between a terminal part 812 provided on a glass substrate 811 of a device substrate 810 and a terminal part 822 provided on a base film 821 of a flexible circuit substrate 820, and pressure is subsequently applied from above. As illustrated in FIG. 9B, when pressure is applied from above the ACF 830 is compression bonded to the device substrate 810 and the flexible circuit substrate 820, and also conductive particles 831 included in the ACF 830 are compressed by the terminal parts 812 and 822, thus electrically connecting the terminal parts 812 and 822 through the conductive particles 831. During the above, the conductive particles 831 are compressed flat, resulting in a large contact surface area between the conductive particles 831 and the terminal parts 812 and 822, thus ensuring stable electrical connection.
The terminal part 812 of the device substrate 810 is extremely thin (for example 0.5 μm) and the glass substrate 811, which is hard and thick, is disposed below the terminal part 812, therefore even if the conductive particles 831 are forcefully compressed during compression bonding, the terminal part 812 is not easily deformed. Furthermore, the terminal part 822 of the flexible circuit substrate 820 is relatively thick (for example 8 μm), and therefore is not easily deformed during compression bonding. By configuring the terminal parts 812 and 822 so that deformation thereof does not occur, the conductive particles 831 between the terminal parts 812 and 822 can be compressed into appropriate flat shapes during compression bonding.
In recent years, there has been development of flexible display devices in which a flexible substrate is used instead of a glass substrate. For example, as illustrated in FIG. 10A, Patent Literature 1 discloses a flexible display device in which a terminal part 912 provided on a flexible substrate 911 of a device substrate 910 and a terminal part 922 provided on a base film 921 of a flexible circuit substrate 920, are electrically connected through conductive particles 931 included in an ACF 930.